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Message-ID:  <55DC28E8.9090405@morningstar2.co.uk>
Date:         Tue, 25 Aug 2015 09:35:52 +0100
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: Catcode changes
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Envelope-To: <rainer.schoepf@GMX.NET>
Status: R

On 25/08/2015 07:05, Joseph Wright wrote:
> On 26/08/2015 00:44, aparsloe wrote:
>> (1) I wanted to use \tl_replace_all:Nnn on a token list that might
>> contain braced groups. Using \tl_set_rescan:Nnn to change the category
>> codes of { and } seemed the most direct way of proceeding. (Then
>> resetting the category codes after replacement with an empty setup.)
> 
> I see what you mean (I have a similar case in siunitx, for historical
> reasons). We'll explore what we can do with this: there are
> mapping-based approaches one can imagine that will enter brace groups.
> (We do that for \tl_lower_case:n, for example). However, for a general
> 'search and replace' I'd be slightly wary as the TeX convention that
> stuff in brace groups is 'special' is quite prevalent. (Depending on
> performance requirements, you might also look at l3regex if you are
> doing the replacement only very rarely.)

It would be useful here to see what your real use case is, as that's
often illustrative.
--
Joseph Wright